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17.5 The Wittig and Related Reactions PowerPoint PPT Presentation


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Main Menu. 17.5 The Wittig and Related Reactions. The Wittig Reaction (formation of alkenes). General Reaction:. R´ and R” can be H or alkyl group. Phosphine oxide. Wittig reagent (a phosphonium ylide ). General Reaction:. base. Formation of Wittig Reagents. A phosphonium salt.

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17.5 The Wittig and Related Reactions

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17 5 the wittig and related reactions

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17.5 The Wittig and Related Reactions

The Wittig Reaction

(formation of alkenes)

General Reaction:

R´ and R” can be H or alkyl group.

Phosphine oxide

Wittig reagent (a phosphoniumylide)


Formation of wittig reagents

General Reaction:

base

Formation of Wittig Reagents

A phosphonium salt

Ph: phenyl

  • The alkyl halides need to have at least one H.

Example:

Potassium tert-butoxide


Mechanism of wittig reaction

Mechanism of Wittig Reaction

oxaphosphetane

betaine


Examples of wittig reaction

Examples of Wittig Reaction

major

minor

Wittig reagents favor the Z (cis) isomer.


Reactions of aldehydes and ketones with horner emmons reagent

Horner-Emmons reaction (general reaction):

Reactions of Aldehydes and Ketones with Horner-Emmons Reagent

R = Et (most common)

Phosphate diester

Horner-Emmons reagent


Formation of horner emmons reagent

Arbuzov (Perkow) reaction:

Formation of Horner-Emmons Reagent

base

Stabilized carboanion

R = alkyl, acyl or R’OC(O)-


Mechanism of horner emmons reaction

Mechanism of Horner-Emmons Reaction

oxaphosphetane

betaine

Water insoluble

Water soluble


Examples of horner emmons reaction

Examples of Horner-Emmons Reaction

> 99%

Horner-Emmons reagents favor the E (trans) isomer.


Learning check

1. What could be the reagent for the following transformation?

Learning Check

2. What should be the product from the following reaction?


Learning check1

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3. What could be the product for the following reaction?

Learning Check


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